In recent years, mobile devices have been required to have many functions such as telephone call, e-mail communication, Internet connection, and game. For this reason, the mobile devices are required to incorporate a large screen display device, and a key operation part having a certain degree of size to enhance operability for a character input. On the other hand, the mobile devices are required to be miniaturized. To meet both of the requirements, there are proposed mobile devices including various mechanisms. For example, a flip-type mobile device including a folding mechanism and a slide-type mobile device including a sliding mechanism are proposed.
Each of Japanese Laid-Open Patent Applications JP-P2003-234809A, JP-P2004-235897A, JP-P2005-269566A, JP-P2005-286994A, and JP-P2006-5564A discloses a mobile device including a sliding mechanism.